If you haven't been vaccinated yet this flu season, here's what you need to know.

By Sarah Klein
January 18, 2018

If news of this has you worried about your own chances of coming down with the virus, here’s a major step you can take to protect yourself (if you haven’t already): Go get a flu shot.

That’s right. No matter what your reason was for putting off your flu vaccine, there’s still time to get one, even if it is past the middle of January already. Here’s why.

RELATED: Here Are 7 Reasons to Stop Putting Off Your Flu Shot

What does the flu shot do?

Getting the flu shot causes your body to produce antibodies that fight the flu. These proteins in the blood are part of the immune system’s natural response to potentially harmful invaders. The vaccine makes it so that if and when you come in with one or more of the viruses that cause the flu, you’re less likely to develop flu symptoms

How effective is the flu shot?

This year, the strain of the flu that seems to be most prevalent is influenza A in the form of H3N2, explains Richard Webby, PhD, a member of the infectious diseases department at St. Jude Children’s Research Hospital. Currently, the Centers for Disease Control and Prevention (CDC) estimates that the 2018 flu shot is about 30% effective against this dominant strain, he says. “We’d like it to be 80, 90, 100% effective, but even at 30% it’s still stopping a good deal of severe disease.” 

Why does the vaccine's effectiveness vary from year to year? Before every flu season, health experts tweak the ingredients in that year's flu vaccine, hoping to make it as effective as possible in protecting against the particular strains of flu-causing viruses that are expected to emerge. If that sounds tricky, that’s because it is.

“We need more research so we can develop an influenza vaccine that works 100% of the time, for 100% of people,” says Pritish K. Tosh, MD, a Mayo Clinic infectious disease physician and researcher. “But we do have a vaccine that is effective in preventing influenza infection and also, in those who get infected, in preventing complications such as hospitalization and even death. While the research is ongoing to create a better vaccine, we need to use the one that we already have.”

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So, is it too late to get the flu shot?

Not at all. Flu season peaks from December to February, but it can last until May, according to the CDC. “The circulating influenza A H3N2 strain will likely continue to be circulating for the next couple months,” Dr. Tosh says, “and if somebody hasn’t gotten infected yet, there’s still time to get infected. Therefore, getting the vaccine may help prevent infection and serious complications.”

In an ideal world, everyone would be vaccinated early in the season. It takes about two weeks for the flu shot to become effective, so the CDC recommends getting your flu shot by the end of October. That way, you’re fully protected by the time flu activity picks up, but not before. “The immunity generated does wane,” Webby says, “so there is some thought that if you get it too early, perhaps by the end of the season you’re not getting the full effect.”

Even after H3N2 circulation slows, other strains, like influenza B, may circulate later in the winter. “It’s not atypical [for] an early influenza A season to be followed by smaller but later influenza B activity,” Webby says. The flu shot also protects against influenza B and, as in years past, pretty effectively, Dr. Tosh adds.

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Where to get the flu shot

If you haven’t been vaccinated yet and you’re finally convinced that it's time, you have lots of options. Your workplace or college might offer free flu shots. But if that was only an October perk, check with a nearby urgent-care center or make an appointment with your primary care physician. You can also your local CVS, Target, Walgreens, or other pharmacy or grocery store; many chains offer free flu shots. Just call ahead of time to make sure the vaccine is available at your preferred location.

Everyone 6 months or older—and yes, even people allergic to eggs!—is encouraged to get the flu vaccine, according to the CDC. So don’t let the frightening flu news stop you. “Even though we’re at the peak right now of influenza season,” Dr. Tosh says, “I would recommend for those who have not gotten vaccinated to do so.”